The leading ignition protection type is crucial for the electrical connection of a pressure sensor with explosion protection. It generally does not necessarily have to be the main one with the stricter requirements. This applies, for instance, for the UHP pressure transducers of the WU series from WIKA. They are designed for use in semiconductor production.
Explosion protection can be an indispensable safety precaution there. This is due to the substances necessary for manufacturing include highly flammable gases. Consequently, there exists a risk of an explosive atmosphere forming.
Explosion protection concept
UHP pressure transducers for such processes must be made with the corresponding safety. As well as their small design and specific process connections, the models WUC-1x and WU-2x have a thorough explosion protection concept. The marking of the instruments provides information on this:
II 3G Ex ec ic IIC T6/T5/T4 Gc X
The abbreviations listed in them mean, in greater detail:
II 3G:
Equipment group 2 (all areas except mining), can be utilized in zone 2 (rare and short-term Ex atmosphere).
Ex ec ic:
Ignition protection types ?ec? (increased safety) and ?ic? (intrinsically safe; zone 2).
?Ex ec? has replaced the ignition protection type ?Ex nA? (non-sparking) since the start of 2022. However, this does not affect the Ex idea of the instruments.
IIC:
Explosion group (here: gases, resistive ignition energy of 40 �J, ideal for hydrogen/acetylene).
T6/T5/T4:
Temperature classes. T6 because the highest requirement means a maximum permissible surface temperature in the Ex environment < 85 �C (max. surface temperature of the WUC-1x and WU-2x: 40 �C).
Gc:
? Hell ? (EPL) for zone 2 per IEC 60079-0
X:
Specific requirements which are listed in the operating instructions (for example, the best mating connector).
?ec? may be the leading ignition protection type
It is noticeable that the marking contains two ignition protection types. However, only one is pertinent for the electrical connection: the leading ignition protection type. In the case of the pressure transducers from the WU series, this is the Ex ec (Ex nA up to 2022) mentioned first and not the stricter Ex ic. This may also be observed in the connection values in the data sheet and operating instructions. Only the specification of the utmost supply voltage UN = 30 V, which is also stated in the IECEx certificate, is pertinent here.
What does the classification ?Ex ic? stand for? It only pertains to the potentiometer of the transducer. The resistive component comes with an intrinsically safe circuit and will therefore be adjusted to correct zero drift during operation. In their overall form, the WU models do not require an intrinsically safe circuit. However, they need to never be disconnected from the circuit during operation or when an Ex atmosphere exists.
Note
More info on the WUC-1x and WU-2x UHP pressure transducers and on the subject of hydrogen are available on the WIKA website. Should you have any questions, your contact will gladly assist you to.
Also read our articles
Ex protection: The most common ignition protection types for sensors in gas hazardous areas
Ex protection: The difference between the zone and division model